Berlin: A Decentralized Approach to Sustainability
Susan Fitzgerald

Green Area Ratio

Berlin is a dense urban area. As such, it cannot address all of the city's ecological needs through the creation of new parks and open space. The Green Area Factor, or Green Area Ratio ("GAR"), focuses on creating green infrastructure on existing public and privately owned parcels by mandating that a percentage of the parcel be green if new building occurs or enhancements to an existing property are made. For the city, this decentralized approach to urban greening is a cost effective way to implement environmental enhancements as the responsibility for funding these enhancements falls on the property owner.

Green Area Ratio Guiding Principles

There are three guiding principles of the GAR. They are:

  1. Modest, decentralized green infrastructure can have a cumulative effect;
  2. Each parcel must in some way contribute to the city's green infrastructure; and
  3. Environmental impacts of development must be mitigated on site.
The GAR allows for a wide variety of greening techniques to be implemented at the discretion of individual parcel owners. Green techniques include green facades, and vegetated courtyards, pictured above.

Green Area Ratio Benefits

The goal of the GAR is to combat what the Germans refer to as "creeping impermeability"--the tendancy for developed land to become more impervious as a result of building additions, increased parking, etc. Under the GAR, such parcel "improvements" can occur only if parcel greening occurs simultaneously, thereby offsetting the effects of development.

The GAR allows for high quality, high density development while also protecting (or even creating new) ecosystems, habitat, landscape character, etc. One of the strengths of the GAR is that it is non-prescriptive--by allowing individual property owners to determine the types of greening that occurs on their parcel, the program actively engages the public in ensuring a sustainable future for the city.

Green Area Ratio Targets

The GAR sets greening targets for different parcel types. These targets are closely paired to zoning and are as follows:

  • Residential: 60% green
  • Mixed use: 40% green
  • Commercial/city center: 30%

All green technologies are not equal--performance varies. To compensate for variations between technologies, the city has developed a weighting system whereby better performing technologies are more highly weighted. The weighting system is based on a variety of ecologic functions, including:

  • capacity for evapotranspiration;
  • ability to trap airborne particulates;
  • capacity to retain/infiltrate stormwater;
  • potential to maintain/support soil function; and
  • creation of habitat for plants and/or animals.


Berlin Weighting Factor for various greening technologies (

In order to determine the percentage of a parcel which is attributable to the GAR requirements, the following formula is used:


(area of technology 1 X weighting) + (area of technology 2 X weighting)...

parcel area

This formula allows parcel owners to combine various greening technologies, in accordance with their personal goals or desires, in order to attain the necessary percentage of greening. This flexibility has made the GAR one of Berlin's most popular and widely accepted environmental initiatives.


Despite the overall popularity of the GAR, some have criticized the program for being too procedurally intense. Initial set up, evaluation of green technologies and public education and outreach required much effort on the city's behalf. In addition, ongoing evaluation of new technologies and monitoring/adminstration of the program may prove costly. Some critics remain leary about prioritizing sustainability and question the value of the city's emphasis on environmental issues.


The GAR's decentralized approach to increasing green infrastructure has many benefits. These include:

  • Improving ecology through private land ownership, thereby saving public funds
  • Promoting green infrastructure throughout the entire city (improving habitat, stormwater management, air quality, open space, etc.);
  • Engaging the public in improving the city's green infrastructure;
  • Fostering a pro-urban approach to sustainable development;
  • Improving the quality of life for Berliners and attracting/retaining people to the city;
  • Improving ecology in the most densely built areas without sacrificing the character of the built environment or existing social structures; and
  • Fostering a city and national identity focused on sustainability.




Next: Incentivizing Stormwater Management

| Case Study Index |

Green Urbanism and Ecological Infrastructure || Instructor, Jack Ahern

Department of Landscape Architecture and Regional Planning
University of Massachusetts, Amherst

Copyright © 2007